The present invention relates to a magnetic recording/reproducing apparatus and, particularly, to a magnetic recording/reproducing apparatus whose video signal reproducing circuit portion is capable of automatically detecting a recording mode of a luminance signal undergoing reproduction, and is capable of changing the characteristics thereof so as to make it suitable to reproduce the luminance signal.
In a recent video tape recorder (referred to as a VTR, hereinafter) for home use, a video signal is recorded according to the luminance signal FM modulation/chrominance signal down conversion system. According to the VHS standard, the carrier frequency is frequency-modulated with a luminance signal within a frequency range from 3.4 MHz to 4.4 MHz and the chrominance signal frequency of 3.58 MHz is converted down to 0.629 MHz to avoid the FM frequency range. Then, theses signals are recorded on a magnetic tape. Therefore, the transmission band of the luminance signal is about 3 MHz and so the horizontal resolution is about 240 lines.
In order to improve the image quality, a High-Band recording system or mode has been proposed, in which the carrier frequency of luminance signal is shifted to the higher frequency side, as disclosed in "1/2 Inches High-Band VTR" Journal of Japan Television Society, May, 1986, pages 36-39.
In reproducing a video signal recorded in the High Band mode using a standard VTR, it is necessary to use a luminance signal processing circuit having characteristics suitable for the High Band mode. In order to make a VTR which is capable of recording and reproducing video signals in both the conventional mode and the High-Band mode, it has been usual to use a luminance signal processing circuit having changeable characteristics and to change the characteristics manually by a user according to the recording mode of the video signal undergoing reproduction.
In the above mentioned prior art in which a user changes manually the characteristics of the luminance signal processing circuit according to the recording mode of the signal undergoing reproduction, a detection of the recording mode is performed by a visual judgement of the user who watches the monitor screen. That is, the switching of the characteristics of the luminance signal processing circuit during reproduction has not been automated as yet.
It may be considered desirable to automate such change of the characteristics of the luminance signal processing circuit by using the difference in the carrier frequency of the luminance signal occurring between the usual mode and the High Band mode. However, there has been no prior art embodying such a scheme. In order to automate the mode switching during reproduction, a circuit construction therefor should not lead to any problem such as errouneous judgement, etc. This has been also not considered as yet.